CVE-2018-11985 in Android
Summary
by MITRE
In all android releases(Android for MSM, Firefox OS for MSM, QRD Android) from CAF using the linux kernel, When allocating heap using user supplied size, Possible heap overflow vulnerability due to integer overflow in roundup to native pointer.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/22/2020
This vulnerability exists within the linux kernel implementation used across various android platforms including MSM variants, firefox os for msm, and qrd android systems. The flaw manifests during heap memory allocation processes where the system accepts user-supplied size parameters to determine memory allocation quantities. The vulnerability stems from an integer overflow condition that occurs during the roundup operation to native pointer alignment, creating a scenario where legitimate memory allocation requests can trigger unexpected behavior. The root cause lies in the kernel's handling of arithmetic operations involving user-provided sizes that, when processed through the roundup function, can exceed the maximum representable value for the integer type being used.
The technical implementation of this vulnerability involves the kernel's memory management subsystem where heap allocations are performed using calculations based on user input. When the system processes user-supplied size values through the roundup function to align memory addresses to native pointer boundaries, an integer overflow can occur. This overflow results in a calculation that produces a smaller value than intended, potentially leading to insufficient memory allocation. The vulnerability becomes exploitable when this miscalculated size value is subsequently used to allocate heap memory, creating conditions where attackers can manipulate the allocation process to cause memory corruption. The integer overflow specifically affects the boundary calculation logic that ensures proper memory alignment, causing the system to allocate memory blocks that are either too small or potentially malformed.
The operational impact of this vulnerability extends across multiple android variants and hardware platforms, making it particularly concerning for mobile device security. Attackers could potentially exploit this weakness to execute arbitrary code within the kernel space, leading to complete system compromise. The vulnerability affects the fundamental memory management capabilities of these systems, potentially allowing for privilege escalation attacks that could enable unauthorized access to sensitive system resources. Since this affects the linux kernel implementation used across different android variants, the attack surface is broad and includes devices running different hardware configurations and software stacks. The exploitation could result in persistent system compromise, data theft, or complete device takeover depending on the execution context and privileges available to the attacker.
Mitigation strategies should focus on implementing robust input validation and integer overflow protection mechanisms within the kernel memory allocation routines. The primary fix involves strengthening the roundup function to prevent integer overflow conditions when processing user-supplied size values, typically through bounds checking and proper overflow detection before arithmetic operations. System administrators and device manufacturers should prioritize applying kernel updates that address this specific integer overflow vulnerability, ensuring that all affected android variants receive the necessary patches. Additionally, implementing runtime protections such as stack canaries, address space layout randomization, and kernel address space layout randomization can help reduce the effectiveness of exploitation attempts. The fix should align with common security practices outlined in the common weakness enumeration framework where such integer overflows are categorized as cwe-190, and should be considered under the attack technique framework where kernel exploits fall under privilege escalation and code execution categories.